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16D drag motor airgap theory?


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#1 Pablo

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Posted 03 June 2018 - 01:31 AM

240px-Jpam.jpg

 

I'm not a drag racer, but a friend requested I build him some drag motors. He gave me a bag full of 16D arms and setups.

I said, "OK, I'm pretty sure I know what to do, but what airgaps do you want?"

Answer: "I don't know".

 

I have the tools and knowledge to build/blueprint 16D type race motors - piece of cake for me.

But zero experience with drag motors (not my cup of tea, sorry)

 

Please help. I don't need advice on how to build motors; I just need to know how much airgap :D

 

I'm not looking for "magic numbers" - just general drag airgap theory as relates to 16D type motors.

Please specify "per side" or total airgap.

 

Thanks

 

Pablo


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#2 idare2bdul

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Posted 03 June 2018 - 02:56 AM

What are his goals? Most Drag racing is Bracket racing where consistency is the key and the slower car gets a head start. If he doesn't red light the other racer has pressure on which often leads to a red light.. If that is the case make sure the motor doesn't have parasitic drag and that the arm turns freely before the brushes are installed. If it is a quarter mile track I liked to set them up with a 12-40 gear ratio. Comes off the line softly and then top ends surprisingly well with just the stock airgap. Just add lead to get the car where you want it. I had a Lexan bodied drag car that had lead piled up so high I just taped the driver to the lead.


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#3 Bill from NH

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Posted 03 June 2018 - 05:54 AM

I would suggest you contact  Doug Azary. Doug has built & rebuilt 100's of 16D drag motors since he retired a couple years ago.


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#4 Pablo

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Posted 03 June 2018 - 01:04 PM

Thanks, Bill :good:


Paul Wolcott

#5 Champion 507

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Posted 03 June 2018 - 01:43 PM

Sorry, I'm having extreme difficulty in concentrating on anything other than the photo in post #1!

 

I just rebuild Parma, ProSlot and Slotworks/Fast Ones 16D's and S16D's as they come from the factory. No air gap change at all.

 

I have 2 drag racing customers in TX. One loves my Parma S16D rebuilds and the other one loves my Parma Deathstar rebuilds. They have consistent cars and do well at the tracks. One guy placed 1st, 2nd, 3rd, 5th, and 7th with my motors in a field of 168 last month, all with stock rebuilt Parma Deathstars with no air gap changes.

 

On a lot of stock, unbalanced Chinese arms, I will static balance them on razor blades. I also check the S16D arms. Some appear to be very well balanced. Others do not, so I attempt to smooth out the rough ones with razor blade balancing.

 

In my opinion, properly setting the car up, knowing how to properly set your dials and hitting a good light take priority over air gaps in a motor. I am strictly talking bracket racing here. I don't have a lot of knowledge about the high powered drag racing. 

 

Back in the 1960's, slot car racing was run what you brung. If you wanted to race something off the wall, you could. But if a guy had scratch built his own frame and bought a rewound motor or did it himself, he probably beat you. With drag racing nowadays, setting a dial levels the playing field. Slot car bracket racing is the closest link we have to the old days. It is literally "run what you brung".


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#6 Pablo

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Posted 03 June 2018 - 03:38 PM

Understood, But these are special wound arms going into PS setups and I have no idea what a stock 16D airgap is.

The gap is going to be whatever I made it.

 

What I do know is, in road course cars, the 16D and S16D arms tend to run surprizing well using what I consider big airgaps.

Like a .518 arm in a .560 hole (.042 airgap/.021 per side).

 

How about I shoot for middle-of-the-road and go with about 30 thou airgap (15 thou per side)?


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#7 mark1

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Posted 03 June 2018 - 08:27 PM

Why not set up a few different air gaps (loose, tight, middle of the road) for him to compare? That could be fun.


Mark Anderson

#8 Pablo

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Posted 03 June 2018 - 08:38 PM

Mark, that is an awesome idea, thank you :good: I'll mark them and he can decide what works best.


Paul Wolcott

#9 Foamy

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Posted 04 June 2018 - 11:36 AM

When we ran Heads-up Super 16-d's, arms were .510 with a .522 airgap. Magnets were shimed in to a tip gap of .260, then honed to .522.


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#10 Pablo

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Posted 04 June 2018 - 02:14 PM

Thanks Dennis :D


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#11 gotboostedvr6

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Posted 05 June 2018 - 03:49 PM

Foamys idea would produce a nearly round hole. Huge difference over shimming and having a oval hole with a variation in the air gap.

Trust me.
I build bad fast 16d motors ;)
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#12 racer4rw

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Posted 13 June 2018 - 04:07 PM

Most rules for class racing have a .560 minimum hole for D can classes.
Rex Westerfield

#13 Pablo

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Posted 13 June 2018 - 05:00 PM

Can you please show me that ruleset? (not saying I don't believe you, since I know zero about drag racing :))

 

How do they enforce that?


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#14 bluecars

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Posted 13 June 2018 - 08:22 PM

I just called Eugene at Talladega and he said down here there are no such rules. He said you can do anything you want to the motor. I remember Bud asking about more air gap to make it come off the line softer, he said you adjust that with a bigger crown gear. .030 (.015 each side) or what ever slug you have that is close. Build on!


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#15 Pablo

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Posted 14 June 2018 - 07:46 AM

Exactly what rules do they use at Talladega?


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#16 bluecars

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Posted 14 June 2018 - 04:22 PM

Must have windshield and be able to make it down the track without de slotting.


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#17 Bud Greene

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Posted 14 June 2018 - 06:53 PM

Rules set for Pearl Miss. is if it makes it down the track its legal


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#18 Pablo

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Posted 14 June 2018 - 07:26 PM

:)


Paul Wolcott

#19 Pablo

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Posted 14 June 2018 - 09:10 PM

Most rules for class racing have a .560 minimum hole for D can classes.

 

What happened, racer4rw, cat got your tongue? ^_^


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#20 Geary Carrier

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Posted 14 June 2018 - 10:39 PM

Rules set for Pearl Miss. is if it makes it down the track its legal

 

Excellent rules...


Yes, to be sure, this is it...


#21 Terry

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Posted 16 June 2018 - 04:21 PM

When using a .518" diameter arm, a .570" - 580" hole is ideal. 

 

This is directly from John Miller at ProSlot.


Terry Watson

#22 gotboostedvr6

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Posted 16 June 2018 - 08:15 PM

I use a .575 to .578 hole with Fx magnets in a Fx setup. And a .585 to .600 hole with Redfox can and Redfox angle magnets.

The fx setup leaves harder, redfox has way more mph. If your looking for special redfox magnets that leave hard and have mph I know a guy.
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#23 idare2bdul

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Posted 11 July 2018 - 12:26 AM

Chewing on the guy for an airgap rule when it was probably in context of road racing? People were pretty nice not making snarky comments about razor blade balancing and a real lack of knowledge about the fact that bracket racing pretty much never has motor rules. Consistency comes from a whole variety of variables with

Car/motor break in

gearing

gluing

tire compound, diameter and width

and the list goes on. 

Most tracks have locals that will help

Start taking notes on what you do, change only one thing at a time. After ten years you will probably get pretty good unless you treat the lights like I do as a random number generator.


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#24 John Good

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Posted 08 August 2018 - 02:02 PM

I'm certainly no expert, but I do run in a weekly heads up list race, running S16Ds with ".518" arms.   I shim my magnets in at least .012 on each side and hone to a total air gap of .855.    For a quarter mile track, that gives me a nice balance of torque and rpm.   We run 85 to 95 gram hardbodies, so the extra power at the start is a plus.  



#25 macman

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Posted 29 September 2018 - 02:35 PM

I like a little shim for brackets in the proslot can... Listen to Foamy, he is extremly knowlegible about slot drag racing.


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